1. Field of the Invention
The present invention relates to steering column assemblies and, more particularly, to steering column assemblies that may be repositioned by the vehicle operator.
2. Description of the Related Art
Steering columns for automobiles and other vehicles that can have the tilt or rake angle of the column and the axial length of the column adjusted by the vehicle operator are well known in the art. A wide variety of such axially and tiltably adjustable steering columns have been developed. An example of one such steering column is shown in FIGS. 1 and 2.
In the prior art steering column assembly depicted in FIGS. 1 and 2, the adjustable steering column assembly 10 includes an upper tubular steering jacket 12 and a lower jacket 13. Upper and lower jackets 12, 13 are telescopingly coupled so that the axial length of the column can be adjusted. A steering shaft 14 extends through the hollow interior of the steering jackets 12, 13. The steering shaft 14 has a steering wheel (not shown) mounted on its projecting end 15 and rotates within steering jackets 12, 13. Steering shaft 14 and steering jackets 12, 13 are adjustably tiltable about pivot member 16 which defines tilt axis 17.
A mounting bracket 18 is formed out of stamped sheet metal and is attached to the vehicle structure with fastener assemblies 19. A compression bracket 20 is also formed out of stamped sheet metal and is attached to upper jacket 12 with welds 21 along opposite sides of jacket 12. Compression bracket 20 fits closely within mounting bracket 18. When steering jackets 12, 13 and steering shaft 14 are tilted about axis 17, mounting bracket 18 remains stationary while compression bracket 20 moves with upper steering jacket 12 within mounting bracket 18. The compression bracket 20 is also displaced relative to mounting bracket 18 when the upper jacket 12 is axially repositioned relative to lower jacket 13 to adjust the overall axial length of the steering column assembly 10.
A locking assembly 22 is provided to secure and release compression bracket 20 relative to mounting bracket 18 to thereby secure steering column 10 in a desired tilt angle at a desired axial length and release steering column 10 for adjustment of the tilt angle and/or axial length.
Locking assembly 22 includes a manually operated lever arm 24. Movement of lever arm 24 between a first position, shown in solid lines in FIG. 1, close to upper jacket member 12 and a second position, shown in dashed lines in FIG. 1, extending outwardly relative to upper jacket 12, operably engages camming member 26. Bolt 28 extends through openings in the sidewalls of mounting bracket 18 and compression bracket 20 and has a nut 30 attached at one end.
Abutment members 32, 34 are located on opposite sides mounting bracket 18 and are coupled with bolt 28 such that as lever 24 is moved from its second position to its first position (shown in solid lines in FIG. 1), camming member 26 moves along camming ramp 27 and biases abutment members 32, 34 closer together to thereby cause abutment members 32, 34 to compress the sidewalls of mounting bracket 18 to firmly engage the sidewalls of compression bracket 20 and thereby secure steering jackets 12, 13 and steering shaft 14 in a desired position. Movement of lever arm to its second position (shown in dashed lines in FIG. 1) increases the distance between abutment members 32, 34 sufficiently to allow compression bracket 20 to move within mounting bracket 20 to allow the operator of the vehicle to reposition compression bracket 20 relative to mounting bracket 18 and thereby adjust the tilt angle and/or axial length of steering column assembly 10. After the operator has repositioned the steering column, the operator will return lever 12 into its first position and thereby secure the steering column at the desired position.
While the adjustable steering column assembly 10 described above performs adequately, the forces applied to the sidewalls of the mounting bracket 18 to inwardly compress the mounting bracket sidewalls also act on the sidewalls of the compression bracket 20 which are formed out of stamped metal sheet stock in the same manner as the sidewalls of the mounting bracket. To increase the resistance of the compression bracket sidewalls to inward compression and thereby provide a more firm engagement between the mounting bracket 18 and the compression bracket 20 when the assembly is in a locked condition, an optional stiffening plate 36 can be welded to the compression bracket 20 as shown in FIG. 2. While the use of such a stiffening plate 36 enhances the resistance of the compression bracket sidewalls to inward compression and thereby improves the performance of the assembly, it also increases the manufacturing complexity of the assembly while still leaving room for further improvement.